Apparatus for making contact discs



March 23, 1965 w. M. MAKI 3,174,257

APPARATUS FOR MAKING coxmcr orscs Filed May 8, 1961 3 Sheets-Sheet 1 March 23, 1965 w. M. MAKI 3,174,257

APPARATUSFOR MAKING CONTACT DISCS FiledMay 8, 1961 3 Sheets-Sheet 3 anu'eniar gVILLIAM M. MAKI.

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March 23, 1965 APPARATUS FOR MAKING CONTACT DISCS Filed May 8. 1961 5 Sheets-Sheet 2 4-4- v 4 47 50 5/ 46 56 so; 5e

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United States Patent 3,174,257 APPARATUS FOR MAIHNG CONTACT DTSQS William M. Maid, Libertyville, 112., assignor to Fansteel Metallurgical Corporation, a corporation of New York Filed May 8, 1961, Ser. No. 108,448 8 Claims. (Cl. 51-99) This invention relates to a machine for producing electrical contacts from rods of tungsten and other refractory metals.

Heretofore, it has been common practice to make electrical contact discs out of a refractory metal such as tungsten by employing complicated cutting techniques or forming operations. Such procedures have been necessary to obtain the desired contacting surface configuration to insure a low resistance junction between contact points and aid in smoother circuit breaking by reducing arcing.

The invention disclosed in this application relates to a machine which automatically produces from a rod of refractory metal electrical contact discs having a conical surface which is thereafter rounded to form a contacting surface.

This is accomplished by directing a rod of contact material down an inclined plane against a stop. When the rod engages the stop, a cutting wheel, disposed at an angle of less than 90 relative to the axis of the rod, is moved into and out of cutting engagement with the rod to sever conically faced discs from the end of the rod. To insure continuous and high speed operation there is provided a simple and highly efi'icient mechanical arrangement which positively moves the rod into engagement with the stop after a disc has been cut therefrom. This device operates with a conventional thin cutting wheel which is only subject to substantial wear along its periphery. This results in lengthening the life of the cutting wheel and is obtained by providing a brake which prevents axial movement of the rod into contact with the side surfaces of the wheel while the cutting wheel is being withdrawn from the rod.

The invention will be understood from the following description taken in connection with the accompanying drawings showing an illustrative embodiment of the invention and in which:

FIGURE 1 is a side elevational view of the machine embodying the invention;

FIGURE 2 is a plan view of the major portion of the machine shown in FIGURE 1;

FIGURE 3 is a side elevational view of the portion of the machine shown in FIGURE 2;

FIGURE 4 is a detailed view of the cutting fixture and rod support;

FIGURE 5 is a cross-sectional view of the cutting fixture and the brake employed for stopping the longitudinal movement of the rod during the withdrawal movement of the cutting Wheel;

FIGURE 6 is a perspective view of the air motor employed for rotating the rod;

FIGURE 7 is a schematic circuit diagram of the various mechanisms for cutting a disc having a conical surface; and

FIGURES 8a, 8b, and 8c are a series of enlarged and exaggerated views illustrating the cutting action that takes place in cutting the conical contact surface.

Generally stated, the machine embodying the invention consists of a rod rotating and feeding assembly A which longitudinally moves a continuously rotated rod R down an inclined ramp into a cutting fixture B where it is cut into electrical contacts by a cutting assembly C. The cutting assembly includes a cutting wheel that is disposed at an angle less than 90 relative to the axis of the rod R.

The movement of the cutting assembly C is regulated by an automatically operated control means D.

The rod rotating and feeding assembly A includes a downwardly inclined, generally U-shaped guideway I mounted on a platform 2. There are located in guide- Way 1 a plurality of longitudinally spaced support cradles 3 which guide the rod R. The support cradles 3 are free to move longitudinally in guideway 1 but are prevented from rotating by pins 4 which are secured to each of the cradles and extend through the opening 1 in the upper portion of guide 1. The rod R is rotated by an air motor 6 (see FIG. 6) which is slidably disposed in guide 1. The motor 6 includes a stator 7 and a rotor 8 that has secured thereto a chuck 9 which secures rod R to rotor 8. Air under pressure is supplied to drive motor 6 through a hose 9 wound on reel 11. The longitudinal movement of the rod R and motor 6 in guide 1 is accomplished by a pulley and weight assembly 12. This pulley and weight assembly 12 consists of a cable 13 that has a weight 14 hanging from one end and is connected at its other end to stator arm 16. This arm is secured to stator '7 of air motor 6 and extends through the opening 1 in guide 1. The cable 13 is wound around pulleys 17, IS, 19, which are rotatably mounted on supports 21, 22 to obtain the desired mechanical advantage.

It can be seen that with the above arrangement, the stator 7 and rod R secured thereto is moved longitudinally in guide 1 by the weight 14 acting through cable 13. During the feeding operation, the freely slidable cradles are engaged by and moved to the end of guide 1 by motor 6.

Referring now to FIG. 4, there is illustrated the cutting fixture B which supports rod R during the cutting operation. Fixture B consists of two mating plates 23, 24 which define aligned openings 23a, 24a. The plates 23, 24 are fastened together by bolt 25 and the assembly there formed is secured to a wedge shaped base plate 28 by bolts 29. The base plate 28 is secured to a machine stand 30 by conventional fastening means (not shown). The upper surface of base plate 28 is parallel to guide 1 so that the aligned openings 23a, 24a in plates 23, 24 are coax al with rod R.

There is fitted into openings 23a a sleeve 26 which guides rod R in fixture B. In aligned opening 24a there is located an insulated bushing 31 within which is disposed a threaded sleeve 32 and stop 33. The stop 33 limits the axial movement of rod R (see FIG. 5). Connected to rod stop 33 by nuts 34, 36 is an electrical control wire 37 which forms part of a control circuit, described hereinafter, that elfects movement of the cutting device C.

The mounting for the cutting device C is shown in FIGS. 1, 2 and 3 and includes a cutting or grinding cutoff wheel 38 which is secured between circular clamps 39, 4% to spindle 41 by bolt 4-2. The cut-ofi Wheel 38 is rotated by spindle drive motor 43 through pulley 44, belt 46 and pulley 47. The spindle 41 is journaled in an intermediate portion of arm 48 of a pivotally mounted cutter support 49. A support 49 for the cutting device C is pivotally mounted on a shaft 51 that is journaled in a pedestal 52 secured to machine stand 30. Secured to the end of support 4% is a plate which is adapted to close switches Stia, Stlb when support 4-9 is moved clockwise and switch 55):: after a predetermined amount of counter clockwise movement. The functions of these switches will be described in detail when discussing FIG. 7 and the method of operation of the apparatus. It is sufiicient to note at this time that switches 59a, 59b will be closed when a predetermined amount of wheel wear has taken place and switch 50c will be closed when rod R has been used up. Pivotally connected to the end portion of arm 48 between ears 54, 56 by a pin 57 is a 3 connecting link 58. The link --58 is positioned by the control system D to pivot support 49 about shaft 51 to move cut-off wheel 38 into and out of engagement with red Rto cut contact discs. Briefly, upward movement of connecting link 58 results in pivotal movement of arm 48, "and pulley '47 about shaft 51 to move cut-oil wheel 38 away from rod R, and downward movement of connecting link 58 moves cut-off Wheel SSiinto cutting engagement with rod R.

In the embodiment shown'in FIG. 1, the control system D employed to position cut-cit wheel through the movement of connecting link 53 includes hydraulicrnotors 61,

62. Motor 61 controls the downward or cutting movement of wheel 38. Motor 62 functions'to raise or'withdraw cut-off wheel '38 after a disc has been out. Also included in the control system is a hydraulic motor 63 which limits the upward movementof cutting assembly C and is adjustable to lower the lower limit of travel of wheel 38 to compensate for wheel wear. The motors 61, 62 include piston rods 61a, 620, respectively, which are secured to a crosshead 67 that is in turn secured to connecting link 58. The piston rod 63a of motor 63 has located thereon limit stops 69, 71 that define the limits of movement of crosshead 67.

The various valves and mechanisms included in control system D for operating the hydraulic motors 61, 62, 63 to regulate the position of cut-off wheel 38 are schematically illustrated in FIG. 7. It can also be appreciated that the structural relationships between the various parts of the 'machine are also diagrammatic in nature in FIG. 7. The particular components employed are conventional in nature and are merely representative of those that could be used to control the movement of cut-off wheel 38. For ease of understanding, the control system will be broken down anddiscussed in (1) terms of the mechanism used and (2) the electrical circuitry involved.

The single acting motor 62, for raising .cut-oif Wheel 38, receiveshigh pressure fluid on the underside of piston 62b from a pump 75 through a solenoid operated valve 77. Valve 77 is a conventional piston type valve and operates to either (1) directfluid from pump 75 and conduit 76 to motor 62 through conduit 78, (2) block off conduit 76 and allow the fluid in conduit 78 to return to reservoir 79 through conduitfitl, or (3) to -by-pass the pump output from conduit 76 to conduit '80 and reservoir 79.

The motor 61 incorporates a closed system in which the flow of fluid from the underside of piston 61b to the top. thereof is limited by restrictor 82. A check valve 81 permits the free flow of fluid between the top of piston 61b and the underside thereof. Thus, it can 'be appreciated that the rate of descent of cut-olf wheel 33 is determined by restrictor 82, but that cut-off wheel 38 can be moved upward at a relatively fast rate by motor 82.

Referring to motor 63, it can be seen that fluid from the underside of piston 63b is free to flow to the topside thereof through check valve 630. Flow in the reverse directionis controlled by a solenoid operated valve 83 which is energized to return support 49 and wheel 38 to the positions they were in before wheel 38 began to wear. The preset space between crosshead 67 and stop 71 is equal to one-half the diameter of rod R plus necessary clearances. Thus, during normal operation of cutting device C, stop 71 is not engaged and motor 63 remains stationary. When wheel wear occurs, there is necessitated a greater downward movement of cutting device C due to the reduced diameter of cut-off wheel 38 which results in crosshead 67 coming into contact with stop 71. This downward movement is permitted by check valve 530 which allows fluid to flow from the underside to the topside of piston 6%. This downward movement continues until rod R is cut through and cut-oif wheel 38 is again retracted. When this occurs, piston 631) will remain in its new position. Stop 69 is provided on rod 63a to limit the upward movement of cutting device C.

Referring now to the electrical circuitry employed in this apparatus, it is noted that the operation of solenoid operated valve 77 and attendant movement of cutting wheel 38 is controlled by relay 90 which includes coil 91 and single-throw switch 92. The coil 91 is in a circuit including power supply 93, rod R and rod stop 33. Thus, movement of rod R into contact with stop 53 will close the circuit to energize coil 91 and when a disc is severed from the rod the circuit willbe opened and coil 91 deenergized. The structure and operation of valve 77 is such that when switch 92 is closed, fluidiiowing from pump is directed to the underside of piston 62b to move cut-off wheel 38 away from rod R; and when switch92 is open, fluid from the underside'of piston 62b flows to reservoir 79.

As previously described, upward movement of cutting assembly C is not aifected by motor 61 but the speed at which piston 62b and cut-ofi wheel 38 moves downward is determined-by the size of 'restrictor 82 which-controls the rate of flow between the upper and lower chambers of motor 61.

Thus it can be seen,-that when rod R engages stop 33, coil 91 is energized to open switch 92 to position valve 77 to exhaust fluid from the underside of piston 62b to eifect downward or cutting movement by the action of gravity on wheel 38. The rate of downward movement isdeterrnined by restrictor 82. After a disc has been severed from rod R and the-circuit is broken, coil 91 is deenergized, switch 92 is closed and cutting device C is moved upward or away from rodR by moving valve 77 to direct fiuid under pressure to the underside of-piston 62b. Fluid in-motor 61 merely moves from one side of piston 61!) to the other through valve 81. It remains to note that switches 5051,5012 are closed when wheel 38 has worn a predeterminedamount (see FIG. 3). The closing of switch 50a allows fluid to return to the underside-of pistonSb. Switch 5064 is set to stay closeda predetermined length cf time by a suitable conventional time delay mechanism. The closing of switch 50b energizes valve 770! to direct fluid to raise and hold support 49 to facilitate replacement of wheel 38. The switch 500 (see FIG. 3) is provided to turn off the machine when support 49 is moved counterclockwise to replace the cutting wheel.

To facilitate withdrawal of cut-off wheel 38 after a disc has been severed from rod R a braking device 100 for temporarily restraining longitudinal movement of rod R is provided. As illustrated inFIG. 5, brake .100 essentially comprises a motor 191 consisting of piston rod 101a and piston 1011). The piston rod 101a extends through a bore 23b in plate 23 and an-opening 26a in rodguide 26 where it contacts rod R. The force exerted by motor 101 is sulficiently large to overcome the longitudinally biasing force exerted on rod R-through the pulley and Wright assembly 12 torprevent longitudinal movement of re R.

Referring again to FIG. 7, it can be seen how brake 106 is tied into the apparatus. The flow of high pressure fluid to motor 101 is controlled by a valve 102 which is operated by a solenoid 102a. The valve 102 has incorporated therein a timing mechanism which functions to deencrgize solenoid 102a when cut-off wheel 38 is moved out of engagement with rod R. Valve 102 is designed so that when solenoid 102a is engaged, fluid is supplied from pump 103 to the underside of piston 101b and when solenoid 102a is deenergized, fluid from the underside of [piston 101b flows back'to reservoir 10.4.

The solenoid 162a is connected in thecircuit including rod R, rod stop 33, and relay so that it is energized when a disc is severed'from rod R. The timing mechanism is set so that after wheel 38 is'moved out of engagement with rod R solenoid 10211 is deenergized and rod 101a is free 'to drop to again allow rod R to be longitudinally moved into engagement with rod stop 33 to restart the cutting cycle.

Briefly, the operation of the apparatus embodying the invention is as'follows:

The rod R is continuously rotated by air motor 6 and is biased longitudinally in the downwardly inclined guide 1 into engagement with rodstop 33 by the pulley and weight assembly 12. When rod R engages stop 33, valve 77 is positioned to'drain fluid'from motor 62 to allow cutting device C and cut-off wheel 38 to move downwardly to cut a disc from red R. The speed at which wheel 38 moves downwardly is determined by restrictor 82. The cut-off wheel 38 is disposed less than a 90 angle relative to rod R with the result that the discs have a conical surface. After the disc has been severed, valve 77 is positioned to supply fluid to motor 62 to raise cut-off wheel 38 away from rod R. The rod is then moved longitudinally into contact with stop 33 to start the cycle all over again. The severing of the disc also results in brake 100 being energized to temporarily prevent rod R from being longitudinally moved into engagement with rod stop 33 until wheel 38 is moved out of engagement with rod R.

The positions of the cut-off wheel during the cutting operation are illustrated in enlarged and exaggerated view in FIGS. 8a, 8b, and 80. It can be seen that the back surface of the contact disc being cut off is slightly concave due to the angular relationship between the cut-off wheel and rod and the diameter of rod R. This concavity can be used to advantage as a pocket for the material used to secure the contact to its support.

With regard to the configuration of the back surface of the contact disc being cut, it remains to note that a disc having a conical back surface can be produced with the disclosed apparatus. This can be accomplished by providing a mechanism such as a releasable collet for holding the end of the rod until the cut-otf wheel 38 cuts through the full diameter of the rod. During this cutting operation, the cutting wheel will first cut a conical surface on the end of the rod, as shown in FIG. 8c, and then after it passes the center of the rod will cut a conical surface on the back of the disc which has been severed from the rod and retained in place by the collet. After the wheel cuts completely through the rod, the wheel will be retracted and the collet opened to release the disc.

While one embodiment of the invention has been described specifically, it will be apparent to those skilled in the art that many alterations and substitutions of mechanical equivalents may be made. For example, the mechanisms disclosed for rotating and longitudinally feeding the red are but a few of the numerous devices that could be employed. Also, the electrical-hydraulic control system used is but representative of various types of electrical, hydraulic or pneumatic control devices which could be used to effect movement of the cutting assembly to cut an elongated rod into discs and prevent longitudinal movement of the rod when desired.

Other equivalents will occur to those skilled in the art and it is, of course, intended to cover by the appended claims all such modifications as fall within the true spirit and scope of the invention.

I claim:

1. A machine for cutting discs having a conical surface from an elongated rod including a downwardly inclined guide means for said rod, means for rotating the rod, means for longitudinally moving the rod, means for limiting longitudinal movement of said rod, a cut-off wheel, control means actuated by the engagement of the rod with the rod limiting means for feeding the cut-off wheel relative to said rod at an angle of less than 90 between the axis of the rod and the direction of feed of the cutoff wheel to cut a disc from the rod, and braking means for preventing longitudinal movement of the rod after a disc has been severed from the rod and until the cut-off wheel has been withdrawn from the rod.

2. A machine for cutting contact discs from an elongated rod of contact material comprising a downwardly sloped guide means for the rod, means disposed in said guide means for rotating the rod, a vertically disposed cut-01f wheel, means including a weight and pulley assembly operatively connected to the rod for longitudinally moving the rod into the cutting area of the cut-off wheel, means for moving the cut-off wheel at an acute angle rel-ative to the axis of the rod to cut from the rod a disc having a conical surface, and braking means for preventing longitudinal movement of the rod during the withdrawal movement of the cut-off wheel after a disc has been severed from the rod.

3. A machine for cutting discs from an elongated rod of contact material comprising a downwardly inclined guide means for the rod, means in said guide means for rotating the rod, a rod limiting means, a pulley and Weight assembly for longitudinally moving the rod into engagement with said rod limiting means, a cutting wheel, and hydraulic control means for feeding the cutting wheel into cutting engagement with said rod at an angle of less than between the axis of the rod and the direction of feed of the cut-ting wheel to cut the rod into discs having a conical surface.

4. A machine for cutting discs from an elongated rod of contact material including a downwardly inclined guide means, means in said guide for rotating the rod, rod limiting means, means for longitudinally feeding the rod into engagement with said rod limiting means, a swingably mounted cut-off wheel, control means responsive to the relationship between the rod and rod limiting means, and hydraulic means responsive to said control means for moving the cutting wheel into cutting engagement with said rod at an angle of less than 90 between the axis of the rod and the direction of feed of the cutting wheel to cut discs from the rod having a conical surface, said hydraulic means including means for compensating for wheel war.

5. In an apparatus for cutting discs having a conical surface from an elongated rod of contact material including a downwardly inclined guide means for the rod, means for rotating the rod, a rod limiting means, a pulley and weight assembly secured to the rod for biasing the rod into engagement with the rod limiting means, a cutoff Wheel, control means responsive to the relationship between the rod and rod limiting means, hydraulic means responsive to said control means for feeding the cutting wheel into and out of engagement with said rod at an angle of less than 90 between the axis of the rod and the direction of feed of the cutting wheel, and brake means for temporarily preventing longitudinal movement of the rod after a disc has been cut therefrom to permit retraction of the cutting wheel.

6. In an apparatus for cutting discs having a conical surface from an elongated rod of contact material comprising a downwardly inclined guide means for the rod, means in said guide means for rotating the rod, a rod limiting means, a pulley and weight assembly secured to the rod for biasing the rod into engagement with the rod limiting means, a cut-ofi wheel at an angle of less than 90 between the axis of the rod and the direction of feed of the cutting wheel, control means responsive to the relationship between the rod and rod limiting means, hydraulic means responsive to said control means for feeding the cutting wheel into and out of engagement with said rod, which hydraulic means includes means for compensating for wheel wear and for limiting the rate of movement of the cutting wheel, and brake means for temporarily preventing longitudinal movement of the rod after a disc has been cut therefrom.

7. A machine for cutting discs from an elongated rod of contact material comprising a downwardly inclined guide means for the rod, a rod limiting means, means for rotating and longitudinally moving the rod in said guide means into contact with said limiting means, a vertically means'responsive to the relationship between the rod and rod limiting means "for moyingthe cutting device into and out of engagement with"said'rod,-'means for compensating for wearing of the cut-ting wheeL-andmeans-for shutting off the machine after a predetermined'wh'eel wear takes place. i y

8. Amachine for cutting'discsfrom an elongated -rod comprising a downwardly inclined guide means for the rod, means for rotating the'rod, acuttingwheel, means to advance the 'rodinto the cutting area of the cutting wheel, and means for relatively feeding the cutting Wheel into cutting engagement with said rod'at an angle df less than 90 between the axis oftherod and the direction of feed of the cutting wheel whereby the rod is cut into discs having a conical surface.

References Cited in the file of this patent UNITED STATES PATENTS 1,122,364 Brown Dec. 29, 1914 2,019,072 Clemens Oct. 29, 1935 2,262,178 Gest et a1. Nov. '11, 1941 2,445,167 Dahl et al July 13, 1948 2,553,147 Roescheise May '15, 1951 2,836,016 Stone May '27, 1958 FOREIGN PATENTS 332,307 GreafBritain July 24, 1930 

8. A MACHINE FOR CUTTING DISCS FROM AN ELONGATED ROD COMPRISING A DOWNWARDLY INCLINED GUIDE MEANS FOR THE ROD, MEANS FOR ROTATING THE ROD, A CUTTING WHEEL, MEANS TO ADVANCE THE ROD INTO THE CUTTING AREA OF THE CUTTING WHEEL, AND MEANS FOR RELATIVELY FEEDING THE CUTTING WHEEL INTO CUTTING ENGAGEMENT WITH SAID ROD AT AN ANGLE OF LESS THAN 90* BETWEEN THE AXIS OF THE ROD AND THE DIRECTION OF FEED OF THE CUTTING WHEEL WHEREBY THE ROD IS CUT INTO DISCS HAVING A CONICAL SURFACE. 